Aren't the cell carriers making things easier in Mexico? With AT&T, as I understand it, if you have a mobile share plan or unlimited plan, you automatically have a Mexico roaming bonus which includes unlimited talk and text to the U.S. and within Mexico, as well as 1G of data, all at no extra cost. I have the iPhone 6 and don't believe I have to do anything special.
Am I missing something?
With AT&T you have to sign up for the Mexico Roaming Bonus plan, and it has to be done on a per line basis.
Other than that, you are correct.